I doubt that the top rail being bent is going to be an issue, as long as it is still strong so you can place your weight on it while boosting yourself up out of teh pool, it's doing it's job, having the flat top level is irrelevant.
I would however take a couple off and inspect teh wall under it to see if it has a kink in it where the top rail slides over it to seat - this may have happened over time.
To paint, I find I have great success painting just about anything with Tremclad, the best way to prep it for a good lasting finish is:
wipre greases off using varsol, let dry, scrape loose paint off and scuff up the remaining surface with 120 grit to 240 grit sandpaper - the higher the number the finer the sandpaper. Clean it once more with varsol, let dry.
Paint on one coat of tremclad primer, this will help get a good bond and smooth out imperfections. Paint the desired color of tremclad, or mix grey and black to try and get a good match to the remaining pool structure (I'm guessing it's a grey shade). Rememeber that once paint dries it darkens a shade.
Another paint I'm really happy with is Krylon fusion - works really well on plastics, but it could become very expensive since it's only available in rattle cans.
Bookmarks